Patent Documents 1 to 3 disclose a flexible package bag provided with a liquid pouring nozzle having a self-sealing one-way function which can prevent penetration of ambient air into the package bag when a liquid material to be packed is poured from a package structure formed by filling and packing the liquid material into the package bag under evacuation. When the liquid material packed in the package bag is poured from the bag, a tip fused portion of the pouring nozzle is removed by tearing with fingers and the like to form a pouring port at the tip of the pouring nozzle, and then the package bag is tilted so as to form a downward posture of the nozzle pouring port. In this case, the tip pouring port of the pouring nozzle made of the flexible laminate films is separated away toward front and rear sides under the action of hydraulic head pressure of the packed liquid material to allow for the required pouring of the packed liquid material.
When the liquid material packed in the bag is poured in such a manner, the main body of the flexible package bag is subjected to shrinkage or collapse deformation by a quantity corresponding to the poured volume associated with the pouring of the packed material without intake of ambient air.
After the predetermined amount of the packed material is poured by tilting the package bag, the pouring is stopped by returning the package to the original standing posture. In the stop of the pouring, the inner surfaces of the nozzle wetted with the packed material are mutually adhered under the intervention of the thin film-like packed material through capillary action or the like over a whole area in a widthwise direction of the front and rear films of the pouring nozzle, namely in a vertical direction thereof at the same time of the pouring stop, whereby the tip pouring port of the nozzle is closed to surely inhibit the penetration of ambient air into the package bag.
In the package bag provided with the pouring nozzle, therefore, the packed material in the bag is sufficiently protected from contacting with ambient air before, during and after the pouring of the packed material, and hence oxidation, contamination and the like of the packed material in the bag can be prevented effectively.
The above-mentioned adhesion between the inner surfaces of the front and rear plastic films constituting the pouring nozzle is automatically carried out by returning the package bag to the standing posture to release the pouring nozzle from the action of hydraulic head pressure to thereby return to the original production form, and further by adsorbing the inner surfaces of the front and rear films wetted with the packed material to each other under an atmosphere of a reduced pressure generated when the packed material in the pouring nozzle flows back to the inside of the main body of the package bag. Such an adhesion is attained more surely when the main body of the package bag shrunk or collapse-deformed with the pouring of the packed material from the package bag acts to render the inside thereof into a reduced pressure based on the elastic restoring force inherent to the package bag.
Here, the tip pouring port of the package bag can be automatically closed and sealed with the returning of the package bag to the standing posture without special operation of the pouring nozzle or the like, and also the excellent self-sealing one-way function of the pouring nozzle can be developed.
On the other hand, the packed material can be poured again by tilting the package bag as described above, while the pouring can be stopped in the same manner as mentioned above. Even in this case, the pouring nozzle can develop the excellent one-way function against penetration of ambient air based on the automatic adhesion and sealing.